1. Field of the Invention
The present invention relates to a semiconductor device. In particular, the present invention relates to an active matrix liquid crystal display device.
2. Description of the Related Art
As a novel semiconductor combining high mobility of crystalline silicon with uniform element characteristics of amorphous silicon, a metal oxide with semiconductor properties, which is called an oxide semiconductor, has attracted attention. The metal oxide is used for various applications; for example, a well-known metal oxide, indium oxide is used for a light-transmitting pixel electrode in a liquid crystal display device, a light-emitting device, or the like. Examples of the metal oxides with semiconductor properties include tungsten oxide, tin oxide, indium oxide, and zinc oxide. It has already been known that such a metal oxide with semiconductor properties is used for a channel formation of a transistor (Patent Documents 1 and 2).